1999 pontiac motana heater
customer says after blower motor replace it does not blow as much thru vent. van was giving to me to check out found that the van blows more on cold or a/c in vent mode than heat. have torn the thing down and found
nothing wrong as in blend doors or plugged heater cores so i am thiking this might be normal. customer says no way.
any suggestions

That vehicle uses a vacuum control system to operate the mode door system. Inspect the vacuum line attached to the actuator and make sure it’s connected. It’s located next to the blower motor. It could have been pinched or pulled off when the blower motor was replaced. Second remove the control assembly from the dash and test the individual vacuum control lines with a hand vacuum pump to see if the mode door changes to its correct possion. If it does replace the control assembly because it has a leak. Here are the specs. On the vacuum control lines. #1 yellow for defrost. #2 red for floor. #3 brown for floor and defrost. #4 is not used. #5 blue for a/c vent. #6 purple for vacuum source. Hope this helps